1. Field of the Invention
The present invention relates to an object positioning method, and more particularly relates to an optimizing method for vehicle cooperative object positioning.
2. Description of Related Art
A technique to install sensors in a vehicle to detect surrounding areas is well developed. For example, the sensors, such as Global Positioning System (GPS), radar, lidar, vehicle dashboard recorder, and etc., can provide different environmental information. For a vehicle itself, the environmental information received from the sensors is limited. For example, with reference to FIG. 9, in a crossroad, the sensors on a first vehicle 101 driving along a longitudinal direction path may observe environmental information along the longitudinal direction. For instance, the sensors on the vehicle can sense objects (such as pedestrians, vehicles, animals, and so on) that fast pass through the crossroad. However, for a second vehicle 102 driving along a horizontal path, the observation of the sensors on the second vehicle 102 is limited by the position and blocked by environmental buildings to have a blind spot. Even if the second vehicle 102 has sensors, the second vehicle 102 may not observe an emergency situation from the object 200 and may hit the object 200. Therefore, if the vehicle relies on the sensors to provide the environmental information only, the blind spot is existed in environmental circumstance.
Accordingly, a vehicle cooperative positioning method is developed. The cooperative idea is to share the information detected by the environmental sensors, such as Road side unit (RSU), or surrounding vehicles, so a local vehicle can receive the information from other vehicles to extend sensing range thereof. With the example in FIG. 9, if the second vehicle 102 can receive the information provided by the first vehicle 101, the object suddenly appearing from a right hand side at the crossroad can be seen by the second vehicle 102 and the second vehicle 102 may have enough time to response.
However, a technical drawback of the conventional cooperative positioning technique is that the accuracy thereof is not good enough. With the example shown in FIG. 10, the first vehicle 101 is the local vehicle, and the second vehicle 102, the third vehicle 103 and the fourth vehicle 104 are neighbor vehicles. For the second vehicle 102 as an example, the second vehicle 102 includes a commercial GPS and a camera. A positioning error of the commercial GPS is about 5-15 meters and the positioning error of the camera is about 5 meters. Therefore, the second vehicle 10 detects a position for itself with a GPS error range A1. When the second vehicle 102 detects the position of the third vehicle 103 by the camera, the position of the third vehicle 103 detected by the camera includes a camera error range A2. Therefore, if the second vehicle 102 shares the detected position information of the third vehicle 103 to the first vehicle 101, the position information of the third vehicle received by the first vehicle 101 includes an error accumulation problem, such as the GPS and a camera accumulating error range A3.
Furthermore, if the first vehicle shares the position information of the third vehicle 103 again to the fourth vehicle 104 and the position error of the first vehicle 101 is also added, more error accumulation values are generated in the position information received in the fourth vehicle 104. Therefore, when the information is transferred and shared many times, the positioning accuracy of the object is decreased and the information is worthless as the reference.